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Liang Z, Ralph-Epps T, Schmidtke MW, Kumar V, Greenberg ML. Decreased pyruvate dehydrogenase activity in Tafazzin-deficient cells is caused by dysregulation of pyruvate dehydrogenase phosphatase 1 (PDP1). J Biol Chem 2024; 300:105697. [PMID: 38301889 PMCID: PMC10884759 DOI: 10.1016/j.jbc.2024.105697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 01/13/2024] [Accepted: 01/19/2024] [Indexed: 02/03/2024] Open
Abstract
Cardiolipin (CL), the signature lipid of the mitochondrial inner membrane, is critical for maintaining optimal mitochondrial function and bioenergetics. Disruption of CL metabolism, caused by mutations in the CL remodeling enzyme TAFAZZIN, results in the life-threatening disorder Barth syndrome (BTHS). While the clinical manifestations of BTHS, such as dilated cardiomyopathy and skeletal myopathy, point to defects in mitochondrial bioenergetics, the disorder is also characterized by broad metabolic dysregulation, including abnormal levels of metabolites associated with the tricarboxylic acid (TCA) cycle. Recent studies have identified the inhibition of pyruvate dehydrogenase (PDH), the gatekeeper enzyme for TCA cycle carbon influx, as a key deficiency in various BTHS model systems. However, the molecular mechanisms linking aberrant CL remodeling, particularly the primary, direct consequence of reduced tetralinoleoyl-CL (TLCL) levels, to PDH activity deficiency are not yet understood. In the current study, we found that remodeled TLCL promotes PDH function by directly binding to and enhancing the activity of PDH phosphatase 1 (PDP1). This is supported by our findings that TLCL uniquely activates PDH in a dose-dependent manner, TLCL binds to PDP1 in vitro, TLCL-mediated PDH activation is attenuated in the presence of phosphatase inhibitor, and PDP1 activity is decreased in Tafazzin-knockout (TAZ-KO) C2C12 myoblasts. Additionally, we observed decreased mitochondrial calcium levels in TAZ-KO cells and treating TAZ-KO cells with calcium lactate (CaLac) increases mitochondrial calcium and restores PDH activity and mitochondrial oxygen consumption rate. Based on our findings, we conclude that reduced mitochondrial calcium levels and decreased binding of PDP1 to TLCL contribute to decreased PDP1 activity in TAZ-KO cells.
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Affiliation(s)
- Zhuqing Liang
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA
| | - Tyler Ralph-Epps
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA
| | - Michael W Schmidtke
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA
| | - Vikalp Kumar
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA
| | - Miriam L Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA.
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2
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Janz A, Walz K, Cirnu A, Surjanto J, Urlaub D, Leskien M, Kohlhaas M, Nickel A, Brand T, Nose N, Wörsdörfer P, Wagner N, Higuchi T, Maack C, Dudek J, Lorenz K, Klopocki E, Ergün S, Duff HJ, Gerull B. Mutations in DNAJC19 cause altered mitochondrial structure and increased mitochondrial respiration in human iPSC-derived cardiomyocytes. Mol Metab 2024; 79:101859. [PMID: 38142971 PMCID: PMC10792641 DOI: 10.1016/j.molmet.2023.101859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 12/06/2023] [Accepted: 12/20/2023] [Indexed: 12/26/2023] Open
Abstract
BACKGROUND Dilated cardiomyopathy with ataxia (DCMA) is an autosomal recessive disorder arising from truncating mutations in DNAJC19, which encodes an inner mitochondrial membrane protein. Clinical features include an early onset, often life-threatening, cardiomyopathy associated with other metabolic features. Here, we aim to understand the metabolic and pathophysiological mechanisms of mutant DNAJC19 for the development of cardiomyopathy. METHODS We generated induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) of two affected siblings with DCMA and a gene-edited truncation variant (tv) of DNAJC19 which all lack the conserved DnaJ interaction domain. The mutant iPSC-CMs and their respective control cells were subjected to various analyses, including assessments of morphology, metabolic function, and physiological consequences such as Ca2+ kinetics, contractility, and arrhythmic potential. Validation of respiration analysis was done in a gene-edited HeLa cell line (DNAJC19tvHeLa). RESULTS Structural analyses revealed mitochondrial fragmentation and abnormal cristae formation associated with an overall reduced mitochondrial protein expression in mutant iPSC-CMs. Morphological alterations were associated with higher oxygen consumption rates (OCRs) in all three mutant iPSC-CMs, indicating higher electron transport chain activity to meet cellular ATP demands. Additionally, increased extracellular acidification rates suggested an increase in overall metabolic flux, while radioactive tracer uptake studies revealed decreased fatty acid uptake and utilization of glucose. Mutant iPSC-CMs also showed increased reactive oxygen species (ROS) and an elevated mitochondrial membrane potential. Increased mitochondrial respiration with pyruvate and malate as substrates was observed in mutant DNAJC19tv HeLa cells in addition to an upregulation of respiratory chain complexes, while cellular ATP-levels remain the same. Moreover, mitochondrial alterations were associated with increased beating frequencies, elevated diastolic Ca2+ concentrations, reduced sarcomere shortening and an increased beat-to-beat rate variability in mutant cell lines in response to β-adrenergic stimulation. CONCLUSIONS Loss of the DnaJ domain disturbs cardiac mitochondrial structure with abnormal cristae formation and leads to mitochondrial dysfunction, suggesting that DNAJC19 plays an essential role in mitochondrial morphogenesis and biogenesis. Moreover, increased mitochondrial respiration, altered substrate utilization, increased ROS production and abnormal Ca2+ kinetics provide insights into the pathogenesis of DCMA-related cardiomyopathy.
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Affiliation(s)
- Anna Janz
- Comprehensive Heart Failure Center, Department of Cardiovascular Genetics, University Hospital Würzburg, Würzburg, Germany
| | - Katharina Walz
- Comprehensive Heart Failure Center, Department of Cardiovascular Genetics, University Hospital Würzburg, Würzburg, Germany
| | - Alexandra Cirnu
- Comprehensive Heart Failure Center, Department of Cardiovascular Genetics, University Hospital Würzburg, Würzburg, Germany
| | - Jessica Surjanto
- Comprehensive Heart Failure Center, Department of Cardiovascular Genetics, University Hospital Würzburg, Würzburg, Germany
| | - Daniela Urlaub
- Comprehensive Heart Failure Center, Department of Cardiovascular Genetics, University Hospital Würzburg, Würzburg, Germany
| | - Miriam Leskien
- Comprehensive Heart Failure Center, Department of Cardiovascular Genetics, University Hospital Würzburg, Würzburg, Germany
| | - Michael Kohlhaas
- Comprehensive Heart Failure Center, Department of Translational Research, University Hospital Würzburg, Würzburg, Germany
| | - Alexander Nickel
- Comprehensive Heart Failure Center, Department of Translational Research, University Hospital Würzburg, Würzburg, Germany
| | - Theresa Brand
- Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany
| | - Naoko Nose
- Comprehensive Heart Failure Center, Department of Nuclear Medicine, University Hospital Würzburg, Würzburg, Germany
| | - Philipp Wörsdörfer
- Institute of Anatomy and Cell Biology, University of Würzburg, Würzburg, Germany
| | - Nicole Wagner
- Institute of Anatomy and Cell Biology, University of Würzburg, Würzburg, Germany
| | - Takahiro Higuchi
- Comprehensive Heart Failure Center, Department of Nuclear Medicine, University Hospital Würzburg, Würzburg, Germany
| | - Christoph Maack
- Comprehensive Heart Failure Center, Department of Translational Research, University Hospital Würzburg, Würzburg, Germany; Department of Medicine I, University Hospital Würzburg, Würzburg, Germany
| | - Jan Dudek
- Comprehensive Heart Failure Center, Department of Translational Research, University Hospital Würzburg, Würzburg, Germany
| | - Kristina Lorenz
- Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany; Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., Dortmund, Germany
| | - Eva Klopocki
- Institute for Human Genetics, Biocenter, Julius-Maximilians-University Würzburg, Würzburg, Germany
| | - Süleyman Ergün
- Institute of Anatomy and Cell Biology, University of Würzburg, Würzburg, Germany
| | - Henry J Duff
- Department of Cardiac Sciences and Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Canada
| | - Brenda Gerull
- Comprehensive Heart Failure Center, Department of Cardiovascular Genetics, University Hospital Würzburg, Würzburg, Germany; Department of Medicine I, University Hospital Würzburg, Würzburg, Germany; Department of Cardiac Sciences and Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Canada.
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3
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Kutschka I, Bertero E, Wasmus C, Xiao K, Yang L, Chen X, Oshima Y, Fischer M, Erk M, Arslan B, Alhasan L, Grosser D, Ermer KJ, Nickel A, Kohlhaas M, Eberl H, Rebs S, Streckfuss-Bömeke K, Schmitz W, Rehling P, Thum T, Higuchi T, Rabinowitz J, Maack C, Dudek J. Activation of the integrated stress response rewires cardiac metabolism in Barth syndrome. Basic Res Cardiol 2023; 118:47. [PMID: 37930434 PMCID: PMC10628049 DOI: 10.1007/s00395-023-01017-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 09/29/2023] [Accepted: 10/14/2023] [Indexed: 11/07/2023]
Abstract
Barth Syndrome (BTHS) is an inherited cardiomyopathy caused by defects in the mitochondrial transacylase TAFAZZIN (Taz), required for the synthesis of the phospholipid cardiolipin. BTHS is characterized by heart failure, increased propensity for arrhythmias and a blunted inotropic reserve. Defects in Ca2+-induced Krebs cycle activation contribute to these functional defects, but despite oxidation of pyridine nucleotides, no oxidative stress developed in the heart. Here, we investigated how retrograde signaling pathways orchestrate metabolic rewiring to compensate for mitochondrial defects. In mice with an inducible knockdown (KD) of TAFAZZIN, and in induced pluripotent stem cell-derived cardiac myocytes, mitochondrial uptake and oxidation of fatty acids was strongly decreased, while glucose uptake was increased. Unbiased transcriptomic analyses revealed that the activation of the eIF2α/ATF4 axis of the integrated stress response upregulates one-carbon metabolism, which diverts glycolytic intermediates towards the biosynthesis of serine and fuels the biosynthesis of glutathione. In addition, strong upregulation of the glutamate/cystine antiporter xCT increases cardiac cystine import required for glutathione synthesis. Increased glutamate uptake facilitates anaplerotic replenishment of the Krebs cycle, sustaining energy production and antioxidative pathways. These data indicate that ATF4-driven rewiring of metabolism compensates for defects in mitochondrial uptake of fatty acids to sustain energy production and antioxidation.
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Affiliation(s)
- Ilona Kutschka
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany
| | - Edoardo Bertero
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany
- Department of Internal Medicine, University of Genova, Genoa, Italy
- Cardiovascular Disease Unit, IRCCS Ospedale Policlinico San Martino - Italian IRCCS Cardiology Network, Genoa, Italy
| | - Christina Wasmus
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany
| | - Ke Xiao
- Institute of Molecular and Translational Therapeutic Strategies, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
- Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM), Nikolai-Fuchs-Straße 1, 30625, Hannover, Germany
| | - Lifeng Yang
- Shanghai Institute of Nutrition and Health, Chinese Academy of Sciences, 320 Yueyang Rd, Shanghai, 200031, China
| | - Xinyu Chen
- Department of Nuclear Medicine, University Clinic Würzburg, Oberdürrbacher Strasse 6, 97080, Würzburg, Germany
| | - Yasuhiro Oshima
- Department of Nuclear Medicine, University Clinic Würzburg, Oberdürrbacher Strasse 6, 97080, Würzburg, Germany
| | - Marcus Fischer
- Division of Pediatric Cardiology and Intensive Care, University Hospital LMU Munich, Marchioninistr. 15, 81377, Munich, Germany
| | - Manuela Erk
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany
| | - Berkan Arslan
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany
| | - Lin Alhasan
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany
| | - Daria Grosser
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany
| | - Katharina J Ermer
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany
| | - Alexander Nickel
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany
| | - Michael Kohlhaas
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany
| | - Hanna Eberl
- Department for Pharmacology and Toxicology, University of Würzburg, Versbacher Strasse 9, 97078, Würzburg, Germany
| | - Sabine Rebs
- Department for Pharmacology and Toxicology, University of Würzburg, Versbacher Strasse 9, 97078, Würzburg, Germany
| | - Katrin Streckfuss-Bömeke
- Department for Pharmacology and Toxicology, University of Würzburg, Versbacher Strasse 9, 97078, Würzburg, Germany
- Clinic for Cardiology and Pneumology, Georg-August University Göttingen and DZHK (German Center for Cardiovascular Research), Partner Site, Göttingen, Germany
| | - Werner Schmitz
- Department of Biochemistry and Molecular Biology, University of Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Peter Rehling
- University Göttingen, Institute of Biochemistry and Molecular Cell Biology, Humboldtallee 23, 37072, Göttingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
| | - Thomas Thum
- Institute of Molecular and Translational Therapeutic Strategies, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
- Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM), Nikolai-Fuchs-Straße 1, 30625, Hannover, Germany
- Rebirth Center for Translational Regenerative Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
| | - Takahiro Higuchi
- Department of Nuclear Medicine, University Clinic Würzburg, Oberdürrbacher Strasse 6, 97080, Würzburg, Germany
| | - Joshua Rabinowitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, 08544, USA
| | - Christoph Maack
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany
- Medical Clinic I, University Clinic Würzburg, Würzburg, Germany
| | - Jan Dudek
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Am Schwarzenberg 15, Haus A15, 97078, Würzburg, Germany.
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4
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Rebs S, Streckfuss-Bömeke K. How can we use stem cell-derived cardiomyocytes to understand the involvement of energetic metabolism in alterations of cardiac function? FRONTIERS IN MOLECULAR MEDICINE 2023; 3:1222986. [PMID: 39086669 PMCID: PMC11285589 DOI: 10.3389/fmmed.2023.1222986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 08/15/2023] [Indexed: 08/02/2024]
Abstract
Mutations in the mitochondrial-DNA or mitochondria related nuclear-encoded-DNA lead to various multisystemic disorders collectively termed mitochondrial diseases. One in three cases of mitochondrial disease affects the heart muscle, which is called mitochondrial cardiomyopathy (MCM) and is associated with hypertrophic, dilated, and noncompact cardiomyopathy. The heart is an organ with high energy demand, and mitochondria occupy 30%-40% of its cardiomyocyte-cell volume. Mitochondrial dysfunction leads to energy depletion and has detrimental effects on cardiac performance. However, disease development and progression in the context of mitochondrial and nuclear DNA mutations, remains incompletely understood. The system of induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CM) is an excellent platform to study MCM since the unique genetic identity to their donors enables a robust recapitulation of the predicted phenotypes in a dish on a patient-specific level. Here, we focus on recent insights into MCM studied by patient-specific iPSC-CM and further discuss research gaps and advances in metabolic maturation of iPSC-CM, which is crucial for the study of mitochondrial dysfunction and to develop novel therapeutic strategies.
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Affiliation(s)
- Sabine Rebs
- Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany
- Clinic for Cardiology and Pneumology, University Medicine Göttingen and DZHK (German Centre for Cardiovascular Research), Göttingen, Germany
| | - Katrin Streckfuss-Bömeke
- Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany
- Clinic for Cardiology and Pneumology, University Medicine Göttingen and DZHK (German Centre for Cardiovascular Research), Göttingen, Germany
- Department of Translational Research, Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Würzburg, Germany
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5
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Pavez-Giani MG, Cyganek L. Recent Advances in Modeling Mitochondrial Cardiomyopathy Using Human Induced Pluripotent Stem Cells. Front Cell Dev Biol 2022; 9:800529. [PMID: 35083221 PMCID: PMC8784695 DOI: 10.3389/fcell.2021.800529] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Accepted: 12/20/2021] [Indexed: 12/17/2022] Open
Abstract
Around one third of patients with mitochondrial disorders develop a kind of cardiomyopathy. In these cases, severity is quite variable ranging from asymptomatic status to severe manifestations including heart failure, arrhythmias, and sudden cardiac death. ATP is primarily generated in the mitochondrial respiratory chain via oxidative phosphorylation by utilizing fatty acids and carbohydrates. Genes in both the nuclear and the mitochondrial DNA encode components of this metabolic route and, although mutations in these genes are extremely rare, the risk to develop cardiac symptoms is significantly higher in this patient cohort. Additionally, infants with cardiovascular compromise in mitochondrial deficiency display a worse late survival compared to patients without cardiac symptoms. At this point, the mechanisms behind cardiac disease progression related to mitochondrial gene mutations are poorly understood and current therapies are unable to substantially restore the cardiac performance and to reduce the disease burden. Therefore, new strategies are needed to uncover the pathophysiological mechanisms and to identify new therapeutic options for mitochondrial cardiomyopathies. Here, human induced pluripotent stem cell (iPSC) technology has emerged to provide a suitable patient-specific model system by recapitulating major characteristics of the disease in vitro, as well as to offer a powerful platform for pre-clinical drug development and for the testing of novel therapeutic options. In the present review, we summarize recent advances in iPSC-based disease modeling of mitochondrial cardiomyopathies and explore the patho-mechanistic insights as well as new therapeutic approaches that were uncovered with this experimental platform. Further, we discuss the challenges and limitations of this technology and provide an overview of the latest techniques to promote metabolic and functional maturation of iPSC-derived cardiomyocytes that might be necessary for modeling of mitochondrial disorders.
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Affiliation(s)
- Mario G Pavez-Giani
- Stem Cell Unit, Clinic for Cardiology and Pneumology, University Medical Center Göttingen, Göttingen, Germany.,German Center for Cardiovascular Research (DZHK), Partner Site Göttingen, Göttingen, Germany
| | - Lukas Cyganek
- Stem Cell Unit, Clinic for Cardiology and Pneumology, University Medical Center Göttingen, Göttingen, Germany.,German Center for Cardiovascular Research (DZHK), Partner Site Göttingen, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells", University of Göttingen, Göttingen, Germany
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6
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Dudek J, Maack C. Mechano-energetic aspects of Barth syndrome. J Inherit Metab Dis 2022; 45:82-98. [PMID: 34423473 DOI: 10.1002/jimd.12427] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 07/28/2021] [Accepted: 08/19/2021] [Indexed: 12/22/2022]
Abstract
Energy-demanding organs like the heart are strongly dependent on oxidative phosphorylation in mitochondria. Oxidative phosphorylation is governed by the respiratory chain located in the inner mitochondrial membrane. The inner mitochondrial membrane is the only cellular membrane with significant amounts of the phospholipid cardiolipin, and cardiolipin was found to directly interact with a number of essential protein complexes, including respiratory chain complexes I to V. An inherited defect in the biogenesis of cardiolipin causes Barth syndrome, which is associated with cardiomyopathy, skeletal myopathy, neutropenia and growth retardation. Energy conversion is dependent on reducing equivalents, which are replenished by oxidative metabolism in the Krebs cycle. Cardiolipin deficiency in Barth syndrome also affects Krebs cycle activity, metabolite transport and mitochondrial morphology. During excitation-contraction coupling, calcium (Ca2+ ) released from the sarcoplasmic reticulum drives sarcomeric contraction. At the same time, Ca2+ influx into mitochondria drives the activation of Krebs cycle dehydrogenases and the regeneration of reducing equivalents. Reducing equivalents are essential not only for energy conversion, but also for maintaining a redox buffer, which is required to detoxify reactive oxygen species (ROS). Defects in CL may also affect Ca2+ uptake into mitochondria and thereby hamper energy supply and demand matching, but also detoxification of ROS. Here, we review the impact of cardiolipin deficiency on mitochondrial function in Barth syndrome and discuss potential therapeutic strategies.
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Affiliation(s)
- Jan Dudek
- Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Würzburg, Germany
| | - Christoph Maack
- Comprehensive Heart Failure Center (CHFC), University Clinic Würzburg, Würzburg, Germany
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7
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Disease Modeling of Mitochondrial Cardiomyopathy Using Patient-Specific Induced Pluripotent Stem Cells. BIOLOGY 2021; 10:biology10100981. [PMID: 34681080 PMCID: PMC8533352 DOI: 10.3390/biology10100981] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/25/2021] [Accepted: 09/26/2021] [Indexed: 12/15/2022]
Abstract
Mitochondrial cardiomyopathy (MCM) is characterized as an oxidative phosphorylation disorder of the heart. More than 100 genetic variants in nuclear or mitochondrial DNA have been associated with MCM. However, the underlying molecular mechanisms linking genetic variants to MCM are not fully understood due to the lack of appropriate cellular and animal models. Patient-specific induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iPSC-CMs) provide an attractive experimental platform for modeling cardiovascular diseases and predicting drug efficacy to such diseases. Here we introduce the pathological and therapeutic studies of MCM using iPSC-CMs and discuss the questions and latest strategies for research using iPSC-CMs.
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8
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McKnight CL, Low YC, Elliott DA, Thorburn DR, Frazier AE. Modelling Mitochondrial Disease in Human Pluripotent Stem Cells: What Have We Learned? Int J Mol Sci 2021; 22:7730. [PMID: 34299348 PMCID: PMC8306397 DOI: 10.3390/ijms22147730] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 07/16/2021] [Accepted: 07/16/2021] [Indexed: 02/06/2023] Open
Abstract
Mitochondrial diseases disrupt cellular energy production and are among the most complex group of inherited genetic disorders. Affecting approximately 1 in 5000 live births, they are both clinically and genetically heterogeneous, and can be highly tissue specific, but most often affect cell types with high energy demands in the brain, heart, and kidneys. There are currently no clinically validated treatment options available, despite several agents showing therapeutic promise. However, modelling these disorders is challenging as many non-human models of mitochondrial disease do not completely recapitulate human phenotypes for known disease genes. Additionally, access to disease-relevant cell or tissue types from patients is often limited. To overcome these difficulties, many groups have turned to human pluripotent stem cells (hPSCs) to model mitochondrial disease for both nuclear-DNA (nDNA) and mitochondrial-DNA (mtDNA) contexts. Leveraging the capacity of hPSCs to differentiate into clinically relevant cell types, these models permit both detailed investigation of cellular pathomechanisms and validation of promising treatment options. Here we catalogue hPSC models of mitochondrial disease that have been generated to date, summarise approaches and key outcomes of phenotypic profiling using these models, and discuss key criteria to guide future investigations using hPSC models of mitochondrial disease.
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Affiliation(s)
- Cameron L. McKnight
- Murdoch Children’s Research Institute, Royal Children’s Hospital, Parkville, VIC 3052, Australia; (C.L.M.); (Y.C.L.); (D.A.E.); (D.R.T.)
- Department of Paediatrics, University of Melbourne, Parkville, VIC 3052, Australia
| | - Yau Chung Low
- Murdoch Children’s Research Institute, Royal Children’s Hospital, Parkville, VIC 3052, Australia; (C.L.M.); (Y.C.L.); (D.A.E.); (D.R.T.)
- Department of Paediatrics, University of Melbourne, Parkville, VIC 3052, Australia
| | - David A. Elliott
- Murdoch Children’s Research Institute, Royal Children’s Hospital, Parkville, VIC 3052, Australia; (C.L.M.); (Y.C.L.); (D.A.E.); (D.R.T.)
- Department of Paediatrics, University of Melbourne, Parkville, VIC 3052, Australia
| | - David R. Thorburn
- Murdoch Children’s Research Institute, Royal Children’s Hospital, Parkville, VIC 3052, Australia; (C.L.M.); (Y.C.L.); (D.A.E.); (D.R.T.)
- Department of Paediatrics, University of Melbourne, Parkville, VIC 3052, Australia
- Victorian Clinical Genetics Services, Royal Children’s Hospital, Parkville, VIC 3052, Australia
| | - Ann E. Frazier
- Murdoch Children’s Research Institute, Royal Children’s Hospital, Parkville, VIC 3052, Australia; (C.L.M.); (Y.C.L.); (D.A.E.); (D.R.T.)
- Department of Paediatrics, University of Melbourne, Parkville, VIC 3052, Australia
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9
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Greenwell AA, Gopal K, Altamimi TR, Saed CT, Wang F, Tabatabaei Dakhili SA, Ho KL, Zhang L, Eaton F, Kruger J, Al Batran R, Lopaschuk GD, Oudit GY, Ussher JR. Barth syndrome-related cardiomyopathy is associated with a reduction in myocardial glucose oxidation. Am J Physiol Heart Circ Physiol 2021; 320:H2255-H2269. [PMID: 33929899 DOI: 10.1152/ajpheart.00873.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Heart failure presents as the leading cause of infant mortality in individuals with Barth syndrome (BTHS), a rare genetic disorder due to mutations in the tafazzin (TAZ) gene affecting mitochondrial structure and function. Investigations into the perturbed bioenergetics in the BTHS heart remain limited. Hence, our objective was to identify the potential alterations in myocardial energy metabolism and molecular underpinnings that may contribute to the early cardiomyopathy and heart failure development in BTHS. Cardiac function and myocardial energy metabolism were assessed via ultrasound echocardiography and isolated working heart perfusions, respectively, in a mouse model of BTHS [doxycycline-inducible Taz knockdown (TazKD) mice]. In addition, we also performed mRNA/protein expression profiling for key regulators of energy metabolism in hearts from TazKD mice and their wild-type (WT) littermates. TazKD mice developed hypertrophic cardiomyopathy as evidenced by increased left ventricular anterior and posterior wall thickness, as well as increased cardiac myocyte cross-sectional area, though no functional impairments were observed. Glucose oxidation rates were markedly reduced in isolated working hearts from TazKD mice compared with their WT littermates in the presence of insulin, which was associated with decreased pyruvate dehydrogenase activity. Conversely, myocardial fatty acid oxidation rates were elevated in TazKD mice, whereas no differences in glycolytic flux or ketone body oxidation rates were observed. Our findings demonstrate that myocardial glucose oxidation is impaired before the development of overt cardiac dysfunction in TazKD mice, and may thus represent a pharmacological target for mitigating the development of cardiomyopathy in BTHS.NEW & NOTEWORTHY Barth syndrome (BTHS) is a rare genetic disorder due to mutations in tafazzin that is frequently associated with infantile-onset cardiomyopathy and subsequent heart failure. Although previous studies have provided evidence of perturbed myocardial energy metabolism in BTHS, actual measurements of flux are lacking. We now report a complete energy metabolism profile that quantifies flux in isolated working hearts from a murine model of BTHS, demonstrating that BTHS is associated with a reduction in glucose oxidation.
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Affiliation(s)
- Amanda A Greenwell
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Alberta, Canada.,Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Alberta, Canada
| | - Keshav Gopal
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Alberta, Canada.,Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Alberta, Canada
| | - Tariq R Altamimi
- Department of Pediatrics, University of Alberta, Alberta, Canada.,Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Alberta, Canada
| | - Christina T Saed
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Alberta, Canada.,Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Alberta, Canada
| | - Faqi Wang
- Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Divsion of Cardiology, Department of Medicine, University of Alberta, Alberta, Canada.,Mazankowski Alberta Heart Institute, University of Alberta, Alberta, Canada
| | - Seyed Amirhossein Tabatabaei Dakhili
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Alberta, Canada.,Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Alberta, Canada
| | - Kim L Ho
- Department of Pediatrics, University of Alberta, Alberta, Canada.,Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Alberta, Canada
| | - Liyan Zhang
- Department of Pediatrics, University of Alberta, Alberta, Canada.,Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Alberta, Canada
| | - Farah Eaton
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Alberta, Canada.,Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Alberta, Canada
| | - Jennifer Kruger
- Health Sciences Laboratory Animal Services, University of Alberta, Alberta, Canada
| | - Rami Al Batran
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Alberta, Canada.,Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Alberta, Canada
| | - Gary D Lopaschuk
- Department of Pediatrics, University of Alberta, Alberta, Canada.,Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Alberta, Canada.,Mazankowski Alberta Heart Institute, University of Alberta, Alberta, Canada
| | - Gavin Y Oudit
- Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Divsion of Cardiology, Department of Medicine, University of Alberta, Alberta, Canada.,Mazankowski Alberta Heart Institute, University of Alberta, Alberta, Canada
| | - John R Ussher
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Alberta, Canada.,Cardiovascular Research Centre, University of Alberta, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Alberta, Canada
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10
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Wang Y, Lei W, Yang J, Ni X, Ye L, Shen Z, Hu S. The updated view on induced pluripotent stem cells for cardiovascular precision medicine. Pflugers Arch 2021; 473:1137-1149. [DOI: 10.1007/s00424-021-02530-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 01/06/2021] [Accepted: 01/29/2021] [Indexed: 12/14/2022]
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11
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Abstract
PURPOSE OF REVIEW Heart failure is among the most prevalent disease complexes overall and is associated with high morbidity and mortality. The underlying aetiology is manifold including coronary artery disease, genetic alterations and mutations, viral infections, adverse immune responses, and cardiac toxicity. To date, no specific therapies have been developed despite notable efforts. This can especially be attributed to hurdles in translational research, mainly due to the lack of proficient models of heart failure limited translation of therapeutic approaches from bench to bedside. RECENT FINDINGS Human induced pluripotent stem cells (hiPSCs) are rising in popularity, granting the ability to divide infinitely, to hold human, patient-specific genome, and to differentiate into any human cell, including cardiomyocytes (hiPSC-CMs). This brings magnificent promise to cardiological research, providing the possibility to recapitulate cardiac diseases in a dish. Advances in yield, maturity, and in vivo resemblance due to straightforward, low-cost protocols, high-throughput approaches, and complex 3D cultures have made this tool widely applicable. In recent years, hiPSC-CMs have been used to model a wide variety of cardiac diseases, bringing along the possibility to not only elucidate molecular mechanisms but also to test novel therapeutic approaches in the dish. Within the last decade, hiPSC-CMs have been exponentially employed to model heart failure. Constant advancements are aiming at improvements of differentiation protocols, hiPSC-CM maturity, and assays to elucidate molecular mechanisms and cellular functions. However, hiPSC-CMs are remaining relatively immature, and in vitro models can only partially recapitulate the complex interactions in vivo. Nevertheless, hiPSC-CMs have evolved as an essential model system in cardiovascular research.
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Affiliation(s)
- Anton Deicher
- Department of Internal Medicine III, University Hospital Heidelberg, INF 410, 69126, Heidelberg, Germany
| | - Timon Seeger
- Department of Internal Medicine III, University Hospital Heidelberg, INF 410, 69126, Heidelberg, Germany.
- German Centre for Cardiovascular Research (DZHK), Partner Site Heidelberg/Mannheim, Heidelberg, Germany.
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12
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Metabolic Alterations Caused by Defective Cardiolipin Remodeling in Inherited Cardiomyopathies. Life (Basel) 2020; 10:life10110277. [PMID: 33187128 PMCID: PMC7697959 DOI: 10.3390/life10110277] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 11/04/2020] [Accepted: 11/06/2020] [Indexed: 12/21/2022] Open
Abstract
The heart is the most energy-consuming organ in the human body. In heart failure, the homeostasis of energy supply and demand is endangered by an increase in cardiomyocyte workload, or by an insufficiency in energy-providing processes. Energy metabolism is directly associated with mitochondrial redox homeostasis. The production of toxic reactive oxygen species (ROS) may overwhelm mitochondrial and cellular ROS defense mechanisms in case of heart failure. Mitochondria are essential cell organelles and provide 95% of the required energy in the heart. Metabolic remodeling, changes in mitochondrial structure or function, and alterations in mitochondrial calcium signaling diminish mitochondrial energy provision in many forms of cardiomyopathy. The mitochondrial respiratory chain creates a proton gradient across the inner mitochondrial membrane, which couples respiration with oxidative phosphorylation and the preservation of energy in the chemical bonds of ATP. Akin to other mitochondrial enzymes, the respiratory chain is integrated into the inner mitochondrial membrane. The tight association with the mitochondrial phospholipid cardiolipin (CL) ensures its structural integrity and coordinates enzymatic activity. This review focuses on how changes in mitochondrial CL may be associated with heart failure. Dysfunctional CL has been found in diabetic cardiomyopathy, ischemia reperfusion injury and the aging heart. Barth syndrome (BTHS) is caused by an inherited defect in the biosynthesis of cardiolipin. Moreover, a dysfunctional CL pool causes other types of rare inherited cardiomyopathies, such as Sengers syndrome and Dilated Cardiomyopathy with Ataxia (DCMA). Here we review the impact of cardiolipin deficiency on mitochondrial functions in cellular and animal models. We describe the molecular mechanisms concerning mitochondrial dysfunction as an incitement of cardiomyopathy and discuss potential therapeutic strategies.
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13
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Parrotta EI, Lucchino V, Scaramuzzino L, Scalise S, Cuda G. Modeling Cardiac Disease Mechanisms Using Induced Pluripotent Stem Cell-Derived Cardiomyocytes: Progress, Promises and Challenges. Int J Mol Sci 2020; 21:E4354. [PMID: 32575374 PMCID: PMC7352327 DOI: 10.3390/ijms21124354] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 06/12/2020] [Accepted: 06/15/2020] [Indexed: 12/12/2022] Open
Abstract
Cardiovascular diseases (CVDs) are a class of disorders affecting the heart or blood vessels. Despite progress in clinical research and therapy, CVDs still represent the leading cause of mortality and morbidity worldwide. The hallmarks of cardiac diseases include heart dysfunction and cardiomyocyte death, inflammation, fibrosis, scar tissue, hyperplasia, hypertrophy, and abnormal ventricular remodeling. The loss of cardiomyocytes is an irreversible process that leads to fibrosis and scar formation, which, in turn, induce heart failure with progressive and dramatic consequences. Both genetic and environmental factors pathologically contribute to the development of CVDs, but the precise causes that trigger cardiac diseases and their progression are still largely unknown. The lack of reliable human model systems for such diseases has hampered the unraveling of the underlying molecular mechanisms and cellular processes involved in heart diseases at their initial stage and during their progression. Over the past decade, significant scientific advances in the field of stem cell biology have literally revolutionized the study of human disease in vitro. Remarkably, the possibility to generate disease-relevant cell types from induced pluripotent stem cells (iPSCs) has developed into an unprecedented and powerful opportunity to achieve the long-standing ambition to investigate human diseases at a cellular level, uncovering their molecular mechanisms, and finally to translate bench discoveries into potential new therapeutic strategies. This review provides an update on previous and current research in the field of iPSC-driven cardiovascular disease modeling, with the aim of underlining the potential of stem-cell biology-based approaches in the elucidation of the pathophysiology of these life-threatening diseases.
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14
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Joseph S, Sharma A, Horne LP, Wood CE, Langaee T, James MO, Stacpoole PW, Keller-Wood M. Pharmacokinetic and Biochemical Profiling of Sodium Dichloroacetate in Pregnant Ewes and Fetuses. Drug Metab Dispos 2020; 49:451-458. [PMID: 33811107 PMCID: PMC11019763 DOI: 10.1124/dmd.120.000330] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 03/16/2021] [Indexed: 11/22/2022] Open
Abstract
Sodium dichloroacetate (DCA) is an investigational drug that shows promise in the treatment of acquired and congenital mitochondrial diseases, including myocardial ischemia and failure. DCA increases glucose utilization and decreases lactate production, so it may also have clinical utility in reducing lactic acidosis during labor. In the current study, we tested the ability of DCA to cross the placenta and be measured in fetal blood after intravenous administration to pregnant ewes during late gestation and labor. Sustained administration of DCA to the mother over 72 hours achieved pharmacologically active levels of DCA in the fetus and decreased fetal plasma lactate concentrations. Multicompartmental pharmacokinetics modeling indicated that drug metabolism in the fetal and maternal compartments is best described by the DCA inhibiting lactate production in both compartments, consistent with our finding that the hepatic expression of the DCA-metabolizing enzyme glutathione transferase zeta1 was decreased in the ewes and their fetuses exposed to the drug. We provide the first evidence that DCA can cross the placental compartment to enter the fetal circulation and inhibit its own hepatic metabolism in the fetus, leading to increased DCA concentrations and decreased fetal plasma lactate concentrations during its parenteral administration to the mother. SIGNIFICANCE STATEMENT: This study was the first to administer sodium dichloroacetate (DCA) to pregnant animals (sheep). It showed that DCA administered to the mother can cross the placental barrier and achieve concentrations in fetus sufficient to decrease fetal lactate concentrations. Consistent with findings reported in other species, DCA-mediated inhibition of glutathione transferase zeta1 was also observed in ewes, resulting in reduced metabolism of DCA after prolonged administration.
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Affiliation(s)
- Serene Joseph
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Abhisheak Sharma
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Lloyd P Horne
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Charles E Wood
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Taimour Langaee
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Margaret O James
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Peter W Stacpoole
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Maureen Keller-Wood
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
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15
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Abstract
Mitochondrial disease presenting in childhood is characterized by clinical, biochemical and genetic complexity. Some children are affected by canonical syndromes, but the majority have nonclassical multisystemic disease presentations involving virtually any organ in the body. Each child has a unique constellation of clinical features and disease trajectory, leading to enormous challenges in diagnosis and management of these heterogeneous disorders. This review discusses the classical mitochondrial syndromes presenting most frequently in childhood and then presents an organ-based perspective including systems less frequently linked to mitochondrial disease, such as skin and hair abnormalities and immune dysfunction. An approach to diagnosis is then presented, encompassing clinical evaluation and biochemical, neuroimaging and genetic investigations, and emphasizing the problem of phenocopies. The impact of next-generation sequencing is discussed, together with the importance of functional validation of novel genetic variants never previously linked to mitochondrial disease. The review concludes with a brief discussion of currently available and emerging therapies. The field of mitochondrial medicine has made enormous strides in the last 30 years, with approaching 400 different genes across two genomes now linked to primary mitochondrial disease. However, many important questions remain unanswered, including the reasons for tissue specificity and variability of clinical presentation of individuals sharing identical gene defects, and a lack of disease-modifying therapies and biomarkers to monitor disease progression and/or response to treatment.
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Affiliation(s)
- S Rahman
- Mitochondrial Research Group, UCL Great Ormond Street Institute of Child Health, London, UK
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